It would be helpful to have more granular control over which suites or tests in a unittest binary are run. We could then do things like separate slow and fast tests and only run the fast tests by default.

I can see the seeds for this support already baked into the unittest framework, just not hooked up here: https://github.com/mongodb/mongo/blob/master/src/mongo/unittest/unittest.cpp#L224 This support exists for the dbtests, so we could do something similar for unittests. This does require a bit more thought as to how to tag a test as "slow" or "do not run by default".